The present invention relates to a method of producing a folded honeycomb structure for a sandwich component and to a foldable sheet-like material.
Although it can be applied to any desired folded structures, the present invention and the problem on which it is based are explained in more detail with reference to folded core structures for sandwich components in aircraft construction.
On account of their good ratio of stiffness and strength to density, composite materials, and in particular so-called sandwich components, have a wide range of applications in the area of aircraft construction.
Sandwich components generally have an upper and a lower outer layer, between which there is, for example, a core structure of vertically running cells of hexagonal cross section, to increase the stiffness.
Another variant of a core structure that is suitable in particular for use in double-shell aircraft fuselages comprises core structures folded from planar semifinished materials. One particular advantage of these structures is that a core that is lightweight, resists buckling, allows drainage, insulates sound and is adapted to the mechanical loads can be folded for a sandwich component, even continuously, from all planar foldable materials with low energy expenditure and with repeating patterns.
The production process for folded honeycomb structures must be performed with adequate accuracy to make it possible for later processing to be carried out without any problems. Apart from the precision that is required, cost-effective production is a second important criterion. In the case of various conventional methods, a sheet-like material to be folded is brought into the desired folded form by male dies or by embedding it between membranes provided with shape-imparting bracing elements. Other methods envisage a pretreatment to weaken the sheet-like material along the desired folding lines. A common characteristic of these methods is that the folded honeycomb structures do not have adequate inherent stability after the folding process, so that it is necessary to support the folded honeycomb structures mechanically by means of fitting moulds, mounts and the like during further method steps, such as for example stabilization by coating or impregnating with resin and subsequent heat treatment for curing. This leads to high production costs and makes it more difficult in particular to produce folded honeycombs in a continuous process.